<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>cdfchi</title>
  </head>
  <body bgcolor="#FFFFFF">
    <center>Scilab Function</center>
    <div align="right">Last update : Dec 1997</div>
    <p>
      <b>cdfchi</b> -  cumulative distribution function chi-square distribution</p>
    <h3>
      <font color="blue">Calling Sequence</font>
    </h3>
    <dl>
      <dd>
        <tt>[P,Q]=cdfchi("PQ",X,Df)  </tt>
      </dd>
      <dd>
        <tt>[X]=cdfchi("X",Df,P,Q);  </tt>
      </dd>
      <dd>
        <tt>[Df]=cdfchi("Df",P,Q,X)  </tt>
      </dd>
    </dl>
    <h3>
      <font color="blue">Parameters</font>
    </h3>
    <ul>
      <li>
        <tt>
          <b>P,Q,Xn,Df</b>
        </tt>: four real vectors of the same size.</li>
      <li>
        <tt>
          <b>P,Q (Q=1-P)  </b>
        </tt>:  The integral from 0 to X of the chi-square distribution. Input range: [0, 1].</li>
      <li>
        <tt>
          <b>X</b>
        </tt>: Upper limit of integration of the non-central chi-square distribution. Input range: [0, +infinity). Search range: [0,1E300]</li>
      <li>
        <tt>
          <b>Df</b>
        </tt>:  Degrees of freedom of the chi-square distribution. Input range: (0, +infinity). Search range: [ 1E-300, 1E300]</li>
    </ul>
    <h3>
      <font color="blue">Description</font>
    </h3>
    <p>
    Calculates any one parameter of the chi-square
    distribution given values for the others.</p>
    <p>
    Formula    26.4.19   of Abramowitz  and     Stegun, Handbook  of
    Mathematical Functions   (1966) is used   to reduce the chi-square
    distribution to the incomplete distribution.</p>
    <p>
    Computation of other parameters involve a seach for a value that
    produces  the desired  value  of P.   The search relies  on  the
    monotinicity of P with the other parameter.</p>
    <p>
    From DCDFLIB: Library of Fortran Routines for Cumulative Distribution
    Functions, Inverses, and Other Parameters (February, 1994)
    Barry W. Brown, James Lovato and Kathy Russell. The University of
    Texas.</p>
  </body>
</html>
